NASA floats Titan boat concept

No one has ever floated a boat on another world, but NASA is now considering doing just that, on Saturn's icy moon Titan. Probing the moon's hydrocarbon lakes could reveal clues to its climate and perhaps even signs of exotic life forms.

Titan's surface is dotted with lakes, making it strangely reminiscent of Earth. But rather than water, the lakes are filled with a mixture of methane and ethane, which are gases on Earth but are liquid at Titan's surface temperature of -180 °C.

NASA is now considering sending a probe to splash down into one of the lakes. It has selected a mission called the Titan Mare Explorer (TiME) as one of three finalists competing for a chance to fly in 2016. The TiME project is led by Ellen Stofan of Proxemy Research in Gaithersburg, Maryland.

In 2023, after a seven-year cruise from Earth, TiME would parachute into a lake in Titan's northern hemisphere called Ligeia Mare. Powered by heat from the decay of an onboard plutonium supply, the probe would bob around the lake's surface and make measurements for about three months.

Titan is the only place in the solar system that appears to have a cycle analogous to the water cycle on Earth, with hydrocarbon rain depositing liquid on the surface, followed by evaporation and more rain.

Rain-lashed probe?

TiME would help reveal details about this cycle by measuring the temperature, humidity and winds at the surface of the lake. With luck, it could be the first probe to experience rain on another world. The probe would also snap pictures of the lake's surface and shorelines and peer up at clouds in the sky.

Though it lacks a means of propulsion, the flying-saucer shaped probe should gradually drift with the breeze, allowing it to sample different parts of the lake. As it did so, it could measure the lake's depth with sonar and taste the brew of chemicals it contains with a mass spectrometer.

That would provide a new window into Titan's intriguing chemistry. Complex carbon-based, or organic, molecules, such as acetylene, are known to form in abundance in the moon's atmosphere and rain down onto the surface.

The organic molecules are likely to get mixed into the lakes and might undergo further chemical reactions there. Some scientists have even speculated that microscopic life forms could live in the lakes, eating acetylene and breathing hydrogen gas.

Searching for signs of life

"Titan is an endpoint on exploring what are the limits to life in our solar system," Stofan told New Scientist. "We're going to be looking for patterns in abundances of compounds to look for evidence for more complex or interesting reactions."

But in order to fly, TiME will have to out-compete two other proposed missions: a seismic monitoring station for Mars and a probe that would hop around the surface of a comet.

NASA has awarded $3 million to each of the three competing teams to flesh out their mission concepts. After a review in 2012, the agency plans to decide which mission will receive the $425 million it needs to fly.

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The TiME mission would send a flying-saucer-shaped probe to float in Ligeia Mare, a 400-kilometre-long hydrocarbon lake on Titan (Image: NASA/JPL/USGS)